Platelet monoamine oxidase and clinical phenomenology of schizophrenia

Platelet monoamine oxidase activity (MAO) was determined in 39 unmedicated chronic schizophrenic patients and 88 normal control subjects. Platelet MAO activity did not distinguish paranoid from nonparanoid patients or patients who met Taylor and Abrams criteria for narrowly defined schizophrenia from other schizophrenics. Enzyme activity was not related to either prognostic scores or age at onset of illness. MAO activity was decreased in patients compared to controls, and was lower in males than in females. Our findings indicate that clinical phenomenology, as defined in the present study, is of limited use in identifying biological subtypes of schizophrenia with deviant platelet MAO activity.     

Platelet monoamine oxidase B activity in Parkinson's disease: A re-evaluation

Summary An increase in platelet monoamine oxidase (MAO) B activity in drug-free parkinsonians (n=6) compared with healthy controls (n=10) has been confirmed using both phenylethylamine (PEA) and dopamine as substrates, reaching statistical, significance in the case of PEA oxidising activity (p<0.05). Thus, certain reports of raised platelet MAO B activity towards PEA but decreased activity towards dopamine in parkinsonians, raising the possibility of the existence of an abnormal form of MAO B in this condition, cannot be supported.     

Platelet monoamine oxidase activity: relation to genetic load of schizophrenia

Platelet monoamine oxidase (MAO) activity is significantly lower in chronic schizophrenic patients with a family history of schizophrenia compared to schizophrenics with no affected relatives and normal controls. These results are consistent with the concept of genetic and biologic heterogeneity in schizophrenia and suggest that the lack of uniformity across previous MAO studies of schizophrenia may be explained in part by the presence of biochemically normal phenocopies.     

Platelet monoamine oxidase molecular activity in demented patients

Blood platelet monoamine oxidase activity, as well as other platelet enzyme activities, have been studied in several neuropsychiatric disorders in an attempt to identify biochemical markers of altered brain function. In this study, we determined both total and molecular monoamine oxidase activity in platelets derived from demented patients, which showed significantly greater enzyme activity than those of the controls. It therefore seems that the high degree of monoamine oxidase activity depends on the increased intrinsic activity of individual enzyme molecules. A significant positive correlation was found between monoamine oxidase activity and the severity of illness, which suggests that monoamine oxidase activity may be a state-dependent marker of neurodegeneration. These findings are discussed with reference to the central nervous system biochemical abnormalities of demented subjects: it may be that Alzheimer-type dementia involves some central biochemical changes that are reflected in certain peripheral tissues (e.g. platelets), or a systemic derangement that also affects the brain.

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Sommario L'attività monoamino-ossidasica (MAO) piastrinica, come pure altre attività enzimatiche trombocitarie, sono state studiate in varie patologie neuropsichiatriche, allo scopo di identificare indici biochimici di un alterato funzionamento cerebrale. In questo lavoro abbiamo determinato l'attività MAO totale e quella molecolare in piastrine di pazienti affetti da demenza tipo Alzheimer, riscontrandone un aumento significativo rispetto ai controlli. Sembra, pertanto, che elevati livelli di attività MAO dipendano da un incremento dell'attività intrinseca delle singole molecole di enzima. Abbiamo osservato vieppiù una correlazione significativa tra attività MAO e gravità di malattia: l'attività MAO quindi può considerarsi, relativamente ad eventi neurodegenerativi, un indice di stato. Questi risultati vengono discussi in riferimento alle alterazioni biochimiche del sistema nervoso centrale occorrenti in pazienti con demenza tipo Alzheimer: può verificarsi che in questa condizione morbosa talune modificazioni biochimiche centrali si riflettano a livello periferico (ad es. nelle piastrine), oppure che alterazioni sistemiche si associno ad un interessamento cerebrale.

     

Neuroleptic drug effect on platelet monoamine oxidase and plasma amine oxidase in schizophrenia

Activity levels of platelet monoamine oxidase (MAO) and plasma amine oxidase (PAO) were determined in eight chronic schizophrenic patients who had been treated with neuroleptic drugs for 3 months. The mean reduction in platelet MAO activity was 18.6%. The extent of decrease was statistically significant. The reduction in enzyme activity was unrelated to serum iron levels. PAO activity was unaltered. The implications for schizophrenia research are discussed.     

Platelet phenolsulphotransferase activity,monoamine oxidase activity and peripheral-type benzodiazepine binding in demented patients

Summary Blood platelet phenolsulphotransferase and monoamine oxidase activities, as well as platelet peripheral-type benzodiazepine binding have been studied in several neuropsychiatric disorders, in order to identify biochemical markers for altered brain functioning. In the present work, we determined platelet phenolsulphotransferase and monoamine oxidase activities in demented patients: they showed significantly higher phenolsulphotransferase and monoamine oxidase activities than controls. A significant positive correlation was found between enzyme activities and severity of illness. In the same subjects, we evaluated platelet peripheral-type benzodiazepine binding: a significant reduction of B_max values was observed in demented patients, whereas K_d values did not substantially differ between the two subject groups.These findings are discussed with reference to central nervous system biochemical abnormalities of demented subjects: it may be that in Dementia of Alzheimer type either some central biochemical changes are reflected in certain peripheral tissues (such as platelets), or a systemic derangement occurs together with a cerebral involvement.     

Platelet monoamine oxidase activity and trace acid levels in plasma of agoraphobic patients

ABSTRACT - Platelet monoamine oxidase activity and plasma trace acid levels in 29 patients classified as agoraphobics was estimated. MAO activity towards p-tyramine and β-phenylethylamine was found to be significantly higher in agoraphobics than in non-agoraphobic depressed patients and healthy controls. In addition plasma p-hydroxyphenylacetic acid levels were low in both agoraphobic and depressed patient groups. All patients were also assessed by Spielberger State Anxiety and the short form of the Beck Depression Inventory scales. No significant correlations could be found between platelet MAO activity or plasma trace acid levels and the psychological scores.     

Platelet aggregation and multiple sclerosis

Measurements of blood platelet aggregation were carried out in 30 patients suffering from multiple sclerosis (MS) and in 15 healthy individuals. Compared with the control group, the MS patients showed an increase in both spontaneous and induced (ADP and serotonin) platelet aggregation. The possible pathogenetic significance of these results is discussed.     

Platelet monoamine oxidase activity in sensation seekers

Personality traits, as assessed by personality inventories, and platelet monoamine oxidase activities have been compared in the following two groups of normal subjects: (1) subjects who either have mountaineering as an active hobby or an interest in mountaineering and (2) subjects not interested in mountaineering. The group of subjects interested in mountaineering were found to be sensation seekers, as assessed by the Zuckerman Sensation Seeking Scale, and to have significantly lower platelet monoamine oxidase activities.     

Platelet monoamine oxidase activity in mentally disordered violent offenders.

The activity of monoamine oxidase (MAO) in blood platelets among criminals undergoing forensic psychiatric examinations was studied. As compulsiveness, disturbed perceptions of reality, etc. are states not known to be related to MAO and yet possibly cause aggressiveness and violence among psychotic patients, we divided the patients into 2 groups, psychotic and nonpsychotic offenders. There was lower MAO activity among violent offenders than among nonviolent offenders. The difference between the violent and nonviolent offenders became greater when the subjects with a history of psychosis were removed. Furthermore, in the group of psychotic offenders, there was no statistical difference between violent and nonviolent individuals in this regard.     

Platelet monoamine oxidase activity is related to MAOB intron 13 genotype

Summary. Monoamine oxidases (MAO) play a critical role in the degradation of endogenous and exogenous amines throughout the body. There are two distinct MAO isoforms, MAO-A and MAO-B, which both are encoded in genes on the X chromosome. Alterations in MAO-B activity have previously been connected with several neurological disorders. Platelet MAO (trbc-MAO) is exclusively of the B-type and the catalytic activity of this enzyme is under strong, yet unknown, genetic control. Specific trbc-MAO activity has been reported to be increased in certain neurodegenerative diseases and to correlate with personality traits such as sensation seeking and impulsiveness. In the present study, we investigated if trbc-MAO activity is associated with genotype at a variable region (A/G dimorphism) in intron 13 of the human gene encoding MAO-B. The MAOB intron 13 allele status and levels of trbc-MAO were determined for 55 Caucasian non-smoking males. Individuals with the "A-allele" displayed significantly lower enzyme activity than individuals with the "G-allele", i.e. 11.4 ± 0.6 nmol/10¹⁰ platelets/min compared with 13.5 ± 0.6 (mean ± SEM, p = 0.019). The present results suggest that the MAOB genotype may be involved in determining trbc-MAO activity. Received July 1, 1999; accepted January 11, 2000     

Platelet monoamine oxidase, plasma dopamine beta-hydroxylase activity, dementia and family history of alcoholism in chronic alcoholics

The authors measured platelet monoamine oxidase (MAO) activity and plasma dopamine beta-hydroxylase activity in 36 male chronic alcoholics during a period of non-abstinence, and in 29 normal controls. The influence of family history, dementia, chronicity of drinking and liver injury on the enzyme activities was also examined by multiple regression analysis. Platelet MAO was significantly lower in the alcoholic group. Both enzyme activities were negatively related to the presence of dementia, while low MAO activity was associated with positive family history (parents, sibs) of alcoholism.     

Platelet monoamine oxidase in healthy 9- and 15-years old children: the effect of gender, smoking and puberty

1. The effect of gender, smoking and pubertal development on platelet monoamine oxidase (MAO) activity was described in a randomly selected, large sample of 9- and 15-years old healthy children.

2. Platelet MAO activity was measured in 1129 children by a radioenzymatic method with β-phenylethylamine as the substrate. Smoking habits were reported in an anonymous questionnaire. Pubertal status was assessed visually using Tanner's stages.

3. Boys, younger children and smokers had significantly lower platelet MAO activity than girls, older children and non-smokers, respectively. Girls in Tanner's stage V for breast and public hair development had significantly lower MAO than girls in stage IV.

4. Differences in gender, age, pubertal status and smoking habits must be taken into account if the relationship between platelet MAO activity, personality and psychiatric disorders is studied in children.

Low platelet monoamine oxidase activity in pathological gambling

Decreased platelet monoamine oxidase (MAO) activity has been reported in association with sensation-seeking personality type and in some mental disorders associated with a lack of impulse control. Pathological gambling itself has been related with both sensation-seeking and reduced impulse control. Platelet MAO activity was investigated in 15 DSM-III-R pathological gamblers from our outpatient clinic. Gamblers had a significantly lower platelet MAO activity than a group of 25 healthy controls. The range of MAO levels in gamblers was also significantly shorter than in controls. In controls, platelet MAO levels showed the previously described negative correlations with sensation-seeking scores but not in gamblers. The findings are consistent with previous studies showing an association of low platelet MAO activity with impulse control disorders and raise some interesting therapeutic alternatives for pathological gambling.     

Platelet monoamine oxidase activity and schizophrenia —A myth that refuses to die?

Summary Platelet monoamine oxidase (MAO) activity was determined using kynuramine as a substrate in a group of schizophrenic patients (n =107), a group of healthy individuals (n =100), and a group of psychiatric patients who were neither schizophrenics nor alcoholics (n =110). No significant difference emerged between the schizophrenics and the other two groups, while a significant reduction in platelet MAO activity in a group of alcoholics (n = 60) was confirmed. Breaking down the schizophrenic group according to course of illness, phenomenology (paranoid-hallucinatory or not) and drug use did not lead to a significant deviation in platelet MAO activity in any of these subgroups. It can also be demonstrated from the literature that the results reached by most research teams question the usefulness of platelet MAO activity as a genetic marker for psychiatric illness.     

Classification of patients with affective disorders using platelet monoamine oxidase activity,serum melatonin and post-dexamethasone Cortisol

Platelet monoamine oxidase activity (MAO), melatonin and Cortisol post-dexamethasone suppression test (DST) were examined in 28 patients with major affective disorder and in 20 controls. MAO activity was lower and Cortisol post-dexamethasone was higher in depressed patients. Platelet MAO activity and Cortisol in depressed and controls yielded high sensitivity (90%) and specificity (89%). The patients were re-examined after 10 years and categorized into affective psychosis or neurotic depression (ICD-9). Multidimensional analysis identified one subgroup coinciding in 92% with affective psychosis and another subgroup coinciding in 87% with neurotic depression. Combination of MAO, melatonin and post-DST Cortisol may be useful in the diagnosis of subgroups of depressed patients and in choice of therapy.     

Platelet MAO activity and monoamine metabolites in cerebrospinal fluid in depressed and suicidal patients and in healthy controls

Platelet monoamine oxidase (MAO) activity and cerebrospinal fluid (CSF) concentrations of 5-hydroxyindoleacetic acid (5HIAA), homovanillic acid (HVA), and 4-hydroxy-3-methoxyphenylglycol (HMPG) were simultaneously measured in 20 currently depressed patients, 11 recovered depressed patients, 15 nondepressed suicide attempters, and 42 healthy control subjects. Both 5HIAA and HVA were positively and significantly correlated to platelet MAO activity in the healthy subjects, but not in any of the patient groups. Suicide attempters had significantly lower CSF 5HIAA than nonsuicidal patients.     

Platelet monoamine oxidase: studies on the rate of heat inactivation in normal and in paranoid and nonparanoid chronic schizophrenic groups.

The heat inactivation curves for platelet monoamine oxidase (MAO) in chronic schizophrenic and normal subjects were virtually identical. There were also no differences found when schizophrenic patients were subgrouped into paranoid and nonparanoid types. However, the MAO from one of the normal subjects showed a substantially greater thermolability than that of any other control or schizophrenic subject.     

Platelet monoamine oxidase activity in relation to alleles of dopamine D4 receptor and tyrosine hydroxylase genes

Human personality characteristics and vulnerability to psychopathology are to a large extent dependent upon genetic factors which have yet to be fully defined. The allele distribution of the dopamine D4 receptor (D4DR) and thrombocyte monoamine oxidase (trbc MAO) activity have both been associated with personality traits which are supposedly related, namely 'sensation seeking’according to Zuckerman and‘novelty seeking’according to Cloninger, respectively. In this report, the D4DR allele distribution and trbc MAO activity were studied in 31 psychiatric patients and 21 control subjects. Trbc MAO activity is a biochemical marker of personality that has been shown to be under strong genetic influence. However, no association between the D4DR alleles and trbc MAO could be observed in this material. To our knowledge, this is the first report comparing these two markers, and based upon the results obtained, we speculate that they may be connected with different types of overlapping personality characteristics. The allele distribution of the tyrosine hydroxylase (TH) gene was also determined. TH is the rate-limiting enzyme in the biosynthesis of catecholamines, and it is believed to be involved in different kinds of psychopathology. No covariation between TH gene alleles and trbc MAO activity or D4DR alleles was observed in this material.